Simplify the following expression: $p = \dfrac{10a}{9} - \dfrac{7a}{6}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $9$ and $6$ $\lcm(9, 6) = 18$ $ p = \dfrac{2}{2} \cdot \dfrac{10a}{9} - \dfrac{3}{3} \cdot \dfrac{7a}{6} $ $p = \dfrac{20a}{18} - \dfrac{21a}{18}$ $p = \dfrac{20a -21a}{18}$ $p = \dfrac{-a}{18}$